Monday, 9 January 2017

Re: Using the dummy0 interface for a local-only service to be broadcasted by Avahi

On Fri, Dec 30, 2016 at 2:44 PM, Till Kamppeter <[email protected]> wrote:
[...]
I also get:

[email protected]:~$ hostname -I
192.168.0.15 192.168.122.1 2804:14c:5ba8:8b97::1 2804:14c:5ba8:8b97:205:1bff:feb0:7395 fd00:1:1::1
[email protected]:~$ hostname -A
till-x1carbon till-x1carbon till-x1carbon till-x1carbon ippusbxd-printers
[email protected]:~$

Does this mean that the first 4 IPs have the host name till-x1carbon and the address fd00:1:1::1 has the host name ippusbxd-printers?

"ping ippusbxd-printers" pings the address fd00:1:1::1.


The man page states for -A:  "Do not make any assumptions about the order of the output."

It simply means that there are a few names you can use *locally* to refer to this system; one of which being "ippusbxd-printers"; as discovered by looking at each configured interface and resolving the address. Nothing more.

Any service that needs to listen to things and care about hostname will need to ask the system on its own what the hostname should be. This is typically done using gethostname() (and it looks like that's what avahi is doing), or looking at files such as /etc/hostname, or asking a daemon like systemd-hostnamed. The closer approximation on the command-line would probably be "getent hosts fd00:1:1::1", but it won't help you if that's not what avahi cares about.


Problems:

1. I would like to assign the name by Zeroconf and not by modifying /etc/hosts. How can I do this.

2. Bonjour/Avahi broadcasting still does not work correctly.

I still register via

error =
    avahi_entry_group_add_service_strlst(bonjour_data->ipp_ref,
                (int)if_nametoindex("ippusbxd"),
        AVAHI_PROTO_UNSPEC, 0,
        dnssd_name,
        "_ipp._tcp", NULL, NULL, 60000,
        ipp_txt);

Set something other than NULL as the "host" parameter? (the second NULL in that call)
 

but the "Address:" entry in the Bonjour record visible in avahi-discover (Interface: ippusbxd -> local -> Internet Printer) still uses the wrong host name:

Address: till-x1carbon.local/fd00:1:1::1:60000

It should be

Address: ippusbxd-printers/fd00:1:1::1:60000

How can I fix this?

I expect that will be fixed when you specify a hostname as you register the service. Otherwise, NULL just tells avahi to use the hostname it already knows, which will be what gethostname() returns.

/ Matt